(7S,9S)-9-Acetyl-9-amino-7-[(2-deoxy-β-D-erythro-pentapyranosyl)oxy]-7,8,9,10-tetrahydro-6,11-dihydroxy-5,12-nephthacenedione hydrochloride represented by the formula (1):
(hereinafter, referred to as amrubicin hydrochloride) has been known to be produced by, for example, the process described in JP 3-5397 B. In addition, amrubicin hydrochloride has been known to have several crystalline forms, a specific crystalline form of which is excellent in heat stability (JP 11-222497 A). However, sometimes, this compound generates as degradation by-products a desaccharification product represented by the formula (2):
and a deamination product represented by the formula (3):
during handling thereof including drying, storage and transfer, though the amounts thereof are slight. In view of medical application, it is of very importance to further suppress the generation of these degradation by-products. In particular, since the deamination product forms insolubles during a production process of a pharmaceutical preparation, suppression of generation thereof is required more than that of the desaccharification product. In view of the above, it has been desired to further develop stabilization and storage methods.